An electrocardiogramis a graphic recording of the electrical activity generated by your heart.The electrical signals produced by your heart are detected by small metaldiscs (electrodes) which are attached to your skin on various parts ofyour body. The detected electrical activity is recorded as a characteristicseries of wavy lines on graph paper.

Why Performed

There is considerable controversyover whether an electrocardiogram is useful in people who do not have symptomsof heart disease. You probably do not need a "routine" ECG unless you havesymptoms suggesting heart disease (unexplained chest pain, shortness ofbreath, dizziness, faintness, or palpitations), or you have several riskfactors for heart disease (high blood pressure, elevated blood cholesterollevels, cigarette smoking, diabetes, or a family history of heart attackbelow the age of 60.

Electrocardiograms are mostoften performed to evaluate unexplained chest pain when a heart attackis suspected. But not every chest pain requires an ECG. Electrocardiogramsare also used to monitor the effectiveness and side effects of certaindrugs which may affect the heart and to check the function of artificialpacemakers (devices inserted into the heart to maintain a normal heartrhythm).

Preparation

• Tell your doctor if you aretaking any medications. Certain medications can influence the interpretationof the ECG.
• There is no need to restrictfood or fluids before the test. All jewelry should be removed from yourneck and wrists.
• You will also need to removeyour clothing above the waist and expose your forearms.
• You may be asked to put on adressing gown for the test.

Procedure

• An electrocardiogram is usuallyperformed by a technician and then interpreted ("read") by a physician.
• It can be performed in a clinic,doctor's office, laboratory, or at your bedside with a portable machine.
• You will be asked to lie ona bed or table. Certain areas on your arms, legs, and chest will be cleanedto remove skin oils and sweat. If the chest area is particularly hairy,it may be necessary to shave small areas to attach the electrode discs.A special ECG paste or small pads soaked in alcohol are placed on the skinto improve electrical conduction.

Next a metal disc (knownas an electrode or ("lead") is attached to the skin on each arm and legwith thick rubber straps or adhesive. A fifth electrode is attached tothe chest by a small rubber suction cup. The "chest lead" is repositionedat six different locations on your chest during the test to measure theelectrical activity from different directions. The electrical activityis converted by the ECG machine into wavy lines on moving graph paper ("atracing").

It is important not to moveor talk during the recording because muscular activity can cause inaccurateresults ("artifacts") on the tracing. Relax, lie still, and breathe normallyunless specifically asked to hold your breath.

The procedure takes 5-10minutes. Sometimes a longer period of recording ("a rhythm strip") is doneto look at your heart's rhythm over a minute or longer.

How Does It Feel?

An ECG is a painless procedure.The electrodes may feel cold when first applied.

Risk:

There is no risk associatedwith an ECG. No electricity passes through your body and therefore, thereis no possibility of receiving an electric shock.

Results:

The different parts of theheartbeat are called the P wave, the QRS complex, the ST segment, and theT wave. Deviations from normal patterns may indicate various types of heartdisease. Conversely, a "normal" ECG can occur even in the presence of heartdisease. Therefore, the ECG should always be interpreted in light of symptoms,history, physical examination, and, if necessary, other test results.

Disorders of Rhythm: Variousirregular rhythm known as arrhythmias, may be detected on an ECG.

However, the ECG in a personhaving a heart attack may initially appear normal or unchanged. Therefore,the ECG may be repeated over several days (serial ECGs) to look for characteristicsigns of heart muscle damage. Other tests, including blood tests for cardiacenzymes, may also be needed to diagnose a heart attack.

Special Considerations

* An electrocardiogram taken atrest may fail to reveal certain abnormalities of the heart. Therefore,additional tests including exercise or stress electrocardiograms have beendeveloped to show the response of the heart to an increased demand to pumpblood.

* Ambulatory (Holter) monitoringrecords the activity of your heart over 24-48 hours rather than just thefew seconds that are recorded on an ECG.